1. Field of the Invention
The present invention relates to a lens barrel which incorporates a shutter unit having a flexible printed wiring board.
2. Description of the Related Art
In conventional lens barrels incorporating a shutter unit, the shutter unit is electrically connected to a controller for controlling the shutter unit via a flexible printed wiring board (flexible PWB), via which a drive signal is supplied from the controller to the shutter unit. Such a flexible PWB has a sufficient length to cover extension/contraction of the lens barrel if the lens barrel is of a extendable type which extends and retracts so that the length thereof is shortest at an accommodation position, and is longer at a photographing position. The flexible PWB is supported so as not to sag in the lens barrel. The flexible PWB for the shutter unit can be twisted by a certain degree in a circumferential direction of the shutter unit about the optical axis, but may be damaged or interfere with peripheral parts if twisted largely. Accordingly, it is often the case that the shutter unit having the flexible PWB is supported by a non-rotational member, e.g., a linearly-guided lens frame to be positioned therein which is guided linearly in the optical axis direction without rotating about the optical axis. Also, the shutter unit having the flexible PWB is often supported by a lens frame for supporting a lens group due to the optical design of the lens barrel.
A lens frame that supports a lens group and also the shutter unit can be made to be rotatable about the optical axis by a certain degree to obtain preferable optical performance and mechanical precision since the flexible PWB that extends from the shutter unit is flexible enough so as to be twistable by a certain amount. However, it is not desirable that the lens frame which supports the shutter unit be rotated by a large amount. Conversely, it is desirable that the rotation range of the lens frame not be restricted by the shutter unit.
It is desirable for a space around the shutter unit in the lens barrel to be utilized to miniaturize the lens barrel when the lens barrel is in an accommodation position. In this case, to prevent the shutter unit from interfering with peripheral parts, it is desirable for the shutter unit not to rotate even if the lens frame which supports the shutter unit rotates when the lens barrel is in the vicinity of the accommodation position thereof.
The present invention provides a lens barrel which supports a shutter unit having a flexible printed wiring board, wherein a large angle of rotation of a lens frame which accommodates the shutter unit can be ensured.
For example, a lens barrel is provided, including an optical system having a front lens group and a rear lens group; a front lens frame which supports the front lens group, and is guided linearly in an optical axis direction without rotating about the optical axis; a rear lens frame which supports the rear lens group; a lens frame drive mechanism for driving the front lens frame and the rear lens frame, wherein the lens frame drive mechanism allows the rear lens frame to rotate relative to the front lens frame when the front lens group and the rear lens group are in respective accommodation positions, and moves the front lens group and the rear lens group together in the optical axis direction while preventing the front lens frame and the rear lens frame from rotating relative to each other when the front lens group and the rear lens group are in respective photographing ranges excluding the respective accommodation positions; a shutter unit having a shutter and a flexible printed wiring board via which a drive signal is transmitted to the shutter, the shutter unit being positioned in the rear lens frame to be rotatable relative to the rear lens frame and to be movable together with the rear lens frame in the optical axis direction; and a shutter unit guide mechanism for linearly guiding the shutter unit in the optical axis direction without rotating the shutter unit regardless of whether the rear lens frame rotates relative to the front lens frame.
The front lens frame can be positioned around the rear lens frame, the shutter unit guide mechanism including a shutter support ring which supports the shutter unit, the shutter support ring being supported in the rear lens frame to be freely rotatable, a linear guide projection which extends outwards in a radial direction from the shutter support ring, and a linear guide groove which is formed on an inner peripheral surface of the front lens frame and in which the linear guide projection is engaged to be movable along the linear guide groove.
A front end of the rear lens frame in the optical axis direction can be open. The rear lens frame can include a movement restriction surface which restricts a rearward movement of the shutter support ring in the optical axis direction in the rear lens frame. The lens barrel can include a shutter pressure plate which is attached at the open front end of the rear lens frame to prevent the shutter unit from moving forward in the optical axis direction with respect to the rear lens frame.
The rear lens frame includes a cylindrical portion which is positioned in the rear lens frame about the optical axis, the shutter support ring having a circular aperture which is rotatably provided around an outer peripheral surface of the cylindrical portion.
The shutter support ring can include a flexible printed wiring board fixing member which supports the flexible printed wiring board. The rear lens frame can include a through-hole through which the flexible printed wiring board fixing member projects from the rear lens frame regardless of a variation in rotational position of the rear lens frame about the optical axis with respect to the front lens frame.
The optical system can include a focusing lens group positioned behind the rear group and guided in the optical axis direction, the lens barrel further including a focusing mechanism for driving the focusing lens group in the optical axis direction in accordance with object-distance information. At least a portion of the focusing mechanism enters inside a portion of the rear lens frame when the front and rear lens groups are in the respective accommodation positions. The shutter unit is formed so that the shutter unit does not interfere with the portion of the focusing mechanism when the focusing mechanism enters inside a portion of the rear lens frame.
It is desirable for the shutter unit to include a cutoff portion which enables the shutter unit not to interfere with the portion of the focusing mechanism.
It is desirable for the lens frame drive mechanism to includes a first cam follower formed on the front lens frame; a second cam follower formed on the rear lens frame; a cam ring including a cam groove in which the first cam follower and the second cam follower are engaged, the cam groove including a photographing section for moving the first cam follower and the second cam follower to move the front lens frame and the rear lens frame in the optical axis direction in the respective photographing ranges, and an accommodation section for moving the first cam follower and the second cam follower to move the front lens frame and the rear lens frame to the respective accommodation positions behind the respective photographing ranges; and a guiding mechanism, provided between the front lens frame and the rear lens frame, for allowing the rear lens frame to rotate relative to the front lens frame when the cam ring is driven to rotate with the front lens frame and the rear lens frame being in the vicinities of the respective accommodation positions thereof, respectively, and for prohibiting the rear lens frame from rotating relative to the front lens frame while allowing the rear lens frame to move only in the optical axis direction relative to the front lens frame when the cam ring is driven to rotate with the front lens frame and the rear lens frame being in the respective photographing ranges excluding the vicinities of the respective accommodation positions.
It is desirable for the front lens frame is positioned around the rear lens frame, the shutter unit guide mechanism including a shutter support ring which supports the shutter unit so that the shutter unit can freely rotate in the rear lens frame; a first linear guide projection which extends outwards in a radial direction from the shutter support ring; and a first linear guide groove which is formed on in an inner peripheral surface of the front lens frame the first linear guide projection being engaged in the linear guide projection to be movable along the first linear guide groove. The guiding mechanism can include a second linear guide groove formed on the front lens frame to extend parallel to the optical axis, a front end of the second linear guide groove being formed as a wide-width engaging portion having a greater width than another portion of the second linear guide groove in a circumferential direction of the front lens frame; and a second linear guide projection formed on the rear lens frame to be engaged in the wide-width engaging portion and the another portion of the second linear guide groove when the front lens frame and the rear lens frame are in the vicinities of the respective accommodation positions thereof and in the respective photographing ranges, respectively. The first linear guide groove and the second linear guide groove are formed on an inner peripheral surface of the front lens frame at different circumferential positions thereon.
It is desirable for the rear lens frame to rotate with a rotation of the cam ring when positioned in the vicinity of the accommodation position thereof.
It is desirable for the lens barrel to include a zoom lens barrel, wherein the lens frame drive mechanism moves the front lens group and the rear lens group to perform a zooming operation in the photographing ranges.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2001-335564 (filed on Oct. 31, 2001) which is expressly incorporated herein by reference in its entirety.